Things to Consider When Lowering Your Vehicle

Front to Back Lowering Mega-Guide

For many enthusiasts, lowering their car is the first and most important modification they do to their vehicles. There is no question that losing a little height will transform the look of your ride, as well as the handling. Heck I don’t think I’ve ever bought a car on the used market that wasn’t dropped on a nice set of wheels! For myself, any many others, it is the bare necessity for any vehicle we own. So all you gotta do is throw a set of coilovers on, crank them down, and lay frame right? Wrong, lowering your car will throw off all your suspension geometry and alignment, as well as create extreme drivetrain angles that can put unnecessary strain on the components. Don’t you worry though, all these things can be fixed with ease.

The modifications you have to do for every single vehicle to compensate for lowering them varies. For the sake of simplicity I will just be covering what to look out for in the most common suspension designs including independent front and rear suspension, as well as solid axle rear suspension.

Almost every car on the road today, excluding trucks and some SUVs, all have some form of independent suspension utilizing at least a lower control arm on each side as well as using rack and pinion steering. This style of suspension allows both the wheels on the axle to cycle through their travel independently of each other, using individual control arms for each side for location. These control arms each hinge from their own individual location causing the camber of the wheels to change throughout the suspensions’ stroke, which is known as camber gain. Power is sent to the wheels through this suspension system via a differential that is hard mounted to the rear subframe between the control arms with axles utilizing constant velocity (CV) or U joints so the axles can move up and down as the suspension compresses and extends.

Alignment

Front

Most vehicles come from the factory aligned at (or close to) zero degrees of camber.

• As the suspension is compressed, whether with more weight , nose dive, or decreasing spring rates or overall lengths, the tops of the wheels tilt inwards, gaining negative camber.
• The Suspension gains positive camber as it is unloaded, or lifted, typically seen only on trucks or Jeeps.
• On average most cars gain about -0.75 degrees of camber with every inch it is lowered, which adds up very quickly. Although negative camber in the front can help tire rollover and increased cornering grip, it will increase tire wear and possibly may cause tramlining, or the tendency of a vehicle's wheels to follow the contours in the surface upon which it runs, making lane control difficult.

Depending on the vehicle and how low you decide to go, you may have enough factory adjustment to be able to correct most of the negative camber. For most people lowering their vehicle 1.5” or more, it may be necessary to consider going for coilovers with existing camber plates, ordering camber plates, or using an aftermarket camber bolt or adjustable control arm to get yourself the alignment you want.

Rear

Rear independent suspension in many ways suffers from the same issues as the front. You will encounter increased camber but in some cases you can run into toe issues, and correcting the alignment specs in general can be more difficult or costly overall. Because most cars typically use a macpherson strut front suspension that has the steering connected to it, there is typically more than enough toe adjustment to correct any issues once lowered, while camber is typically easily corrected using camber plates. Unfortunately, in the majority of cases, the rear is not so easily aligned.

• Most independent rear suspension systems use multilink rear suspension, usually consisting of a lower and upper control arm, a traction or trailing arm, and often a toe arm.
• Because the suspension is located by individual control arms managing their own individual alignment curves, camber plates would do little to nothing to adjust static camber effectively.
• Furthermore without the benefit of the massive adjustment tie rods provide, toe adjustment is typically limited. Never fear, most vehicles either eccentric alignment bolts, adjustable arms, or both available in the aftermarket.

Some vehicles like the BRZ/FRS/GT86 also run into an issue that once lowered where the rear wheel has a tendency to sit closer to the rear bumper at ride height, which can cause rubbing issues. To correct this I used an adjustable traction arm, also known as a rear trailing arm, to help pull the wheel back into the center of the wheel well.

Body Roll / Roll Center

Similarly, as you go lower you also lower your center of gravity. As your COG is lowered it gets closer to your roll center, or the theoretical point in which your chassis rolls from, which will minimize a vehicles tendency to roll. In fact, if the roll center and center of gravity are at the same point the vehicle will have no body roll at all and not need sway bars. So where does it go south?

• Some body roll works towards better loading your tires, if your roll center and center of gravity are too close it will be difficult to generate any grip and the car will easily slide. Furthermore, you can begin to experience bump steer, especially on MacPherson strut style front suspension.
• Typically as the vehicle is lowered, the control arm angles will become more extreme, while the tie rods will often be at less extreme angles. If the steering arms or tie rods do not cycle through the suspensions travel on a parallel path to the control arms the vehicle will have a tendency to change toe. Example: Driving over a bump and the tires are forced to steer, thus the name bumpsteer.
• It is incredibly important for all wheel drive and rear wheel drive vehicles have their rear roll center and center of gravity set precisely as getting your roll center wrong will lead to the vehicle being unable to load the tires effectively under throttle input as well as creating the potential for increased wheel hop.
• There are many kits that correct bump steer and roll center simultaneously with tie rods and a roll center correcting ball joint, spindle, strut spacer, or a lowered steering knuckle which will help make your control arms and tie rods more parallel and adjust your roll center to a more effective height. These kits are often called Roll Center Adjusters or RCAS, Bumpsteer kits, or drop knuckles.
• It is incredibly important for all wheel drive and rear wheel drive vehicles have their rear roll center and center of gravity set precisely as getting your roll center wrong will lead to the vehicle being unable to load the tires effectively under throttle input as well as creating the potential for increased wheel hop.

Drivetrain Angle

Independent Suspension

Your suspension and steering angles are not the only things to worry about though if you want to go really low. If the vehicle has independent suspension with Constant Velocity (CV) joint axles, it will be incredibly important to make sure your CV axle angle is not too extreme. Many vehicles, like early Mistubishi Evos, run into an issue that once lowered the CV axle will actually bind and limit suspension travel as well as prematurely wear the CV joints. Another great example being my own 2013 Subaru BRZ lost an axle and left me stranded at just 75,000 miles because it has been lowered on coilovers with drop knuckles in the rear. Other ZN6 chassis owners have ran into premature axle failure lowered as little as 1.5”. To rmake sure I would never shred a CV joint due to being too low again, I installed Parts Shop Max differential and subframe risers that help lift the subframe and differential so that the angle of the CVs would not be so extreme. This is a common modification for Nissan S, Z, and R chassis models, as well as some BMWs, while vehicles like the Honda S2000 frequently use an axle spacer to help solve this issue.

Constant Velocity joints or CVs typically can only handle between 22 and 31 degrees of articulation angle, so it is imperative to make sure your axles are less than 10 degrees off being parallel with the ground at your chosen ride height to minimize any chance of drivetrain bind or failure.

Solid Axles: A Lost Art?

Just because solid axles are old technology, does not mean they can not work well. In fact, solid axles are much easier to tune the geometry of, as well as correct any issues with being lowered. The venerable solid axle, located by a four link and panhard bar, has been at home in countless muscle cars including mustangs through 2014 as well as cars that have become legendary for their handling like the AE86. Furthermore, it is the number one rear suspension and drivetrain of choice by drag racers.

So what happens when you lower your solid axle car? Well your axle will no longer be centered under the car to start. As your suspension cycles through its travel, the panhard bar causes some lateral movement of the axle. Additionally, the panhard bar will no longer be parallel with the axle, minimizing its effectiveness. To correct this, you would use an adjustable panhard bar as well as a drop bracket to mount the panhard bar at a more effective angle.

Another characteristic of solid axle suspension is that of the pinion or drive shaft angle to change throughout the suspension, meaning once lowered, the driveline angle will no longer be ideal at the new ride height. Incorrect driveline angle can lead to bind, axle wrap and wheel hop, as well as increased drivetrain vibration and wear. To correct this most people install adjustable upper and lower control arms to properly set their pinion angle. To correct roll center, and effectively tune the vehicles tendency to squat or jack under load, you would use a traction bracket, or dropped lower control arm mount to effectively raise the axle relative to the control arm height. This will also work to help correct some driveline angle and do away with a lot of wheel hop.